Its probably because theres no built in stabilizer. Mspaint is super old as you probably know, and I'm pretty sure that's the reason why it has no stabilizer. You would be better off using the line tool (that's what I do, I really like the polygon look) but if you really want to fix it, you would be better off using an emulator sort of thing, like Jspaint. I use it instead of regular Mspaint just because, maybe it will solve your problem?
DependencyWalker will help you. Open mspaint.exe inside it, and it will scan for all required dependencies for it to run. It can give you a minimum files required list too.
The new paint app hasn't been released yet and the Win10 update they were talking about comes out next year. There was an early version leaked, but Microsoft were able to disable it.
edit:
According to this article, it appears that if you are using an insider (beta) build, you are able to download the new paint app from the store.
Was doodling on a paper and then I was like oh this would be cool in paint. Open google type in "paint" find jspaint.app, fast-forward to a few minutes later "hey there must be a sub for that" and here we are! Hello people of r/mspaint!